This section is intended to provide a background or context to the invention disclosed below. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise explicitly indicated herein, what is described in this section is not prior art to the description in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:
ABS Almost-Blank Subframes
AWT Alternate Wireless Technology
dB decibels
CRS Common Reference Signal
dB decibels
DL DownLink (from base station to user equipment)
DMRS Demodulation Reference Signal
EESM Exponential Effective SIR Mapping
eICIC enhanced Interference Control Interference Coordination
eNB or eNode B evolved Node B (LTE base station)
ePDCCH Enhanced Physical Downlink Control CHannel
HetNet Heterogeneous Network
LPS Low-Power Subframe
LTE Long Term Evolution
MCS Modulation and Coding Scheme
MIB Master Information Block
MME Mobility Management Entity
NCE Network Control Element
OFDM Orthogonal Frequency Division Multiplex
PCC Primary Component Carrier
PDCCH Physical Downlink Control CHannel
PDSCH Physical Downlink Shared Channel
RB resource block
Rel Release
RSRP Reference Signal Received Power
SCC Secondary Component Carrier
SGW Serving GateWay
SINR Signal to Interference plus Noise Ratio
SIR Signal to Interference Ratio
SON Self Optimizing Network
UE User Equipment
HetNet (e.g., AWT) is increasingly being used, e.g., to increase capacity in certain areas. HetNet typically involves adding additional access points within a macro cell where the access points form smaller cells that “underlay” the macro cell. That is, the additional access points form cells having smaller coverage than the macro cell, but can provide, e.g., additional capacity within that smaller coverage. Thus, with HetNet, the number of sites increases dramatically and each site has a smaller footprint (e.g., relative to a macro cell).
The underlying cells and their corresponding base stations have names that correspond to the size of the coverage. For instance, a pico cell typically has a larger coverage than does a femto cell. Common names used for these smaller cells include (in order of coverage from larger to smaller) micro, pico, and femto cells. In addition to these smaller cells, there are also relay cells. Relay cells decode and store information received wirelessly, and forward the information wirelessly to user equipment (or vice versa, from the user equipment to the base station).
In HetNet, cell range extension can be used to offload more UEs to a pico cell even though a UE has better SINR to a macro cell. In cell range extension, a biasing parameter is used so that more UEs connect to, e.g., a pico cell. However, there are problems with cell range extension for HetNet.